Study and modeling of continuous pressing of oilseeds

Ce travail de thèse vise à améliorer la compréhension des phénomènes physiques se produisant durant le pressage en continu des graines oléagineuses et à développer un modèle phénoménologique décrivant le comportement mécanique de la matière au cours de sa compression le long de la vis. Les expérimentations ont été réalisées sur des graines de colza, en utilisant un pilote de presse à vis instrumenté (Reinartz, Allemagne). Deux arrangements de vis différents ont été étudiés et comparés, de manière à observer l’influence de la géométrie sur les performances opératoires, le développement des contraintes à l’intérieur de la cage et les propriétés mécaniques du gâteau de pressage. L’instrumentation de la presse a permis de générer des données précises de débits d’huile et de gâteau, capacité de traitement, rendement d’extraction et consommation d’énergie spécifique, pour des vitesses de rotation de la vis comprises entre 0 et 18,2 tr/min. Des profils de pression, teneur en huile et vitesse de déplacement ont également été déterminés pour les deux arrangements de vis, pour caractériser le fonctionnement de la presse. Ces données ont permis d’identifier une alternance de zones de compression et de transport le long de la vis, avec une présence éventuelle de phénomènes de reflux. Une représentation simplifiée a été proposée, pour décrire le pressage continu comme une succession de d’étapes de pressage discontinu. En se basant sur la théorie de filtration/consolidation, le coefficient de consolidation, le module de compressibilité et la résistance spécifique du gâteau de pressage ont étés calculés pour chaque zone de compression. Les propriétés mécaniques du gâteau de pressage ont finalement été utilisées pour développer une relation semi-empirique permettant de prédire le débit d’huile et le rendement d’extraction de la presse. Les résultats expérimentaux correspondent aux données estimées avec une précision satisfaisante.This work was devoted to better understand the physical phenomena occurring during oilseeds expression in continuous screw presses and to develop a phenomenological model describing the compression behavior of the press cake along the screw. Experiments were conducted on canola seeds, using an instrumented pilot screw press (Reinartz, Germany). Two different screw arrangements were studied and compared in order to observe the influence of the geometry on the operating performances, the constraints development in the barrel and the press cake mechanical properties. Press monitoring provided accurate data about oil and cake flowrates, treatment capacity, extraction yield and specific energy consumption, for screw rotation speeds ranging between 0 and 18.2rpm. Pressure, deoiling and displacement velocity profiles were also determined for both arrangements to characterize the press operation. These data allowed to identify the alternation of compression and transport sections along the screw, possibly supplemented by oil reflux. A simplified representation was proposed, describing continuous pressing as a succession of multiple batch pressing steps. Based on the filtration/consolidation theory, the consolidation coefficient, compressibility modulus and press cake specific resistance were calculated in each compression sections. The press cake mechanical properties were finally used to develop a semi-empirical relation predicting the press oil flowrate and extraction yield. Experimental results fitted the estimated data with satisfactory accuracy

Residence time distribution and flow pattern modeling of oilseeds in a pilot screw press

Mechanical expression is widely applied for oil recovery from oilseeds using continuous screw presses. Despite significant recent advances in the field of press design and automation, it remains difficult to predict the press performances based on the theoretical approaches, and more experimental investigations are needed to clarify and characterize the seeds flow and expression behavior in the press. Residence Time Distribution (RTD) is a frequently used tool in chemical engineering to characterize the material flow by simple tracer tests. In this paper, we explore the feasibility of using RTD for the screw presses, in order to check the flow patterns homogeneity and identify the possible deviations depending on the press geometry and the operating conditions. Both theoretical modeling and experimental investigation are conducted for two different screw press designs (Reinartz and Olexa), and at the different rotation speeds. An original and reliable experimental methodology was developed by using erucic acid as tracer in the form of pulse injection and gas chromatography as detection method. Experimental results coupled with statistical calculations showed the influence of the screw geometry and the rotation speed on the seeds flow inside the press. The matter displacement was much faster and the experimental residence time was very close to the theoretical one indicating more homogeneity and less dispersion in the Olexa arrangement in comparison to the Reinartz arrangement. The higher variance observed at lower rotation speed (2.4 rpm) suggested the presence of flow defects like mixing and axial dispersion in the press. To complete the experimental work, axial dispersion model was applied, and allowed obtaining the valuable information, such as axial dispersion degree and distribution functions. Obtained results can be very useful to predict the performance of existing screw presses and design more efficient industrial equipments

Quelques éléments marquants de la 107ème réunion annuelle de l’AOCS (Salt Lake City, 1–4 mai 2016)

La 107ème réunion annuelle de l’AOCS s’est tenue à Salt Lake City (USA) du 1 au 4 mai 2016. Comme à son habitude, ce congrès a balayé l’ensemble des domaines de la recherche concernant de près ou de loin les lipides avec pas moins de 11 sessions techniques en parallèle. À noter la mise en place pour la première fois d’une véritable session « Protein and Co-products » soulignant la montée en puissance des recherches sur les protéines. L’objectif de cet article n’est pas de faire un compte-rendu exhaustif mais plutôt de présenter les avancées remarquables dans les différentes sessions

Quelques éléments marquants de la 107ème réunion annuelle de l’AOCS (Salt Lake City, 1–4 mai 2016)

The 107th AOCS Annual Meeting and Expo held in Salt Lake City (Utah, USA) from 1st to 4th May 2016. As usual, this congress overviewed research in areas about lipids with up to 11 technical sessions in parallel. Note the holding for the first time a full session "Protein and Co-products" highlighting the rise of research on proteins. The aim of this article is not to provide a comprehensive account but to present the remarkable advancements within the sessions.La 107ème réunion annuelle de l’AOCS s’est tenue à Salt Lake City (USA) du 1 au 4 mai 2016. Comme à son habitude, ce congrès a balayé l’ensemble des domaines de la recherche concernant de près ou de loin les lipides avec pas moins de 11 sessions techniques en parallèle. À noter la mise en place pour la première fois d’une véritable session « Protein and Co-products » soulignant la montée en puissance des recherches sur les protéines. L’objectif de cet article n’est pas de faire un compte-rendu exhaustif mais plutôt de présenter les avancées remarquables dans les différentes sessions

Mechanical Dyssynchrony Combined with Septal Scarring Reliably Identifies Responders to Cardiac Resynchronization Therapy

Background and aim: The presence of mechanical dyssynchrony on echocardiography is associated with reverse remodelling and decreased mortality after cardiac resynchronization therapy (CRT). Contrarily, myocardial scar reduces the effect of CRT. This study investigated how well a combined assessment of different markers of mechanical dyssynchrony and scarring identifies CRT responders. Methods: In a prospective multicentre study of 170 CRT recipients, septal flash (SF), apical rocking (ApRock), systolic stretch index (SSI), and lateral-to-septal (LW-S) work differences were assessed using echocardiography. Myocardial scarring was quantified using cardiac magnetic resonance imaging (CMR) or excluded based on a coronary angiogram and clinical history. The primary endpoint was a CRT response, defined as a ≥15% reduction in LV end-systolic volume 12 months after implantation. The secondary endpoint was time-to-death. Results: The combined assessment of mechanical dyssynchrony and septal scarring showed AUCs ranging between 0.81 (95%CI: 0.74–0.88) and 0.86 (95%CI: 0.79–0.91) for predicting a CRT response, without significant differences between the markers, but significantly higher than mechanical dyssynchrony alone. QRS morphology, QRS duration, and LV ejection fraction were not superior in their prediction. Predictive power was similar in the subgroups of patients with ischemic cardiomyopathy. The combined assessments significantly predicted all-cause mortality at 44 ± 13 months after CRT with a hazard ratio ranging from 0.28 (95%CI: 0.12–0.67) to 0.20 (95%CI: 0.08–0.49). Conclusions: The combined assessment of mechanical dyssynchrony and septal scarring identified CRT responders with high predictive power. Both visual and quantitative markers were highly feasible and demonstrated similar results. This work demonstrates the value of imaging LV mechanics and scarring in CRT candidates, which can already be achieved in a clinical routine